Air siren giving sharp tones of short duration



Dec. 26, 1950 E. s. RUSSELL 2,535,520

AIR SIREN GIVING SHARP TONES OF SHORT DURATION Filed Aug. 5, 1948 2 Sheets-Sheet l lnvenlor l l'rfle-if fuaripuasell zgw A ltorneyg Dec. 26, 1950 E. s. RUSSELL 2,535,520

AIR SIREN GIVING SHARP TONES OF SHORT DURATION Patented Dec. 26, 1950 AIR SIREN GIVINGSHARP TONES OF SHORT DURATION Ernest Stuart Russell, Wraysbury, England Application August 5, 1948, Serial No. 42,567 In Great Britain August 14, 1947 '6 Claims. 1

This invention relates to electric sirens of the rotary type in which a rotor having substantially radial blades and a rim having'a number of ports creates by centrifugal force a pressure of air against the rim of a stator having the same number of ports. The rotation of the rotor in the stator has the effect of alternately opening and closing the stator ports to the egress of air and so creates a noise varying in frequency with the .nui berof ports and the speed of rotation. Such siren hereinafter will be designated as of the type specified.

The acceleration and deceleration of the retors of such sirens produce wailing notes such as adopted for air raid warnings and since the times of acceleration and deceleration are long due to the high inertia of the electrical and sound rtors such sirens cannot be used to give sharp and distinct signa s or signals of short duration.

This difficulty has been partially overcome in sirens constructed by the applicant in which the air intake of a standard siren is fitted with a mechanically or electrically operated valve or shutter.

By allowing the siren to rotate continuously whilst the shutter is open and closed in a prearranged time sequence it is possib e to obtain distinctive signals. The same effect can be obtained by switching the current on to and off from a circuit in which the siren motor and the shutter operating solenoid are in parallel. Shutters on the discharge side of the stator have also been tried but these do not prevent the egress of sound unless each port is completely sealed and if machined to the necessary fine sliding fits they bei stator and rotor permits an internal circulation of air and sound is emitted from the siren through the inlet aperture.

Whilst the above systems present a partial solution to the problem of proper signalling by rotary sirens they have a serious defect in that it is impossible to prevent the siren making considerable noise even when the intake or discharge shutters are completely sealed, the signals being recognisable due to the difference in volume of sound when the shutter is closed and not to the total absence of sound at this time.

In sirens of the present invention all objectionable sound between signals can be suppressed so that rotary sirens may be used for all types of sound signalling such as fog and manoeuvring signals aboard ship, fog signals for buoys, harbours, and so forth. and any kind of Morse code signalling and the like.

According to the invention a standard siren of the rotary type (without the n cessity for any valve or shutter either on the intake ordischarge) is fitted "with a cover which envelope both the'suction discharge portions of thesiren so as to prevent ingr ss of air and e ress to outside the cover when this is pressed against a flange or the eq ival nt on the siren stator. This satisfactorily prevents the emission'of noise except when the cover is slid or lifted until it uncovers the dis harge ports on the siren stator and allows ingress of outside air to the siren rotor. Even greater efficiency can be obtained if the cover is arra ng d to obstructentirely the inlet to the rotor when the cover is sealed on to the stator so as to prevent any internal circulation of air except th t within the actual stator.

Since it is undesirable that the cover be a sliding fit on the outside of the stator, it is kept some distance away from it leaving an annular air space and is s pported on one or more pins or the like sliding in suitably designed bearings. If desired spr ngs may be used to maintain the cover in the closed position: alternatively it may be held there by its own or added weight.

For the p rpose of opening the cover pressure may be applied to it at a number of equidistant points around its p riphery or at the centre.

In the preferred forms of the invention the rotor sha t is made hollow so that an operating rod sup orted on external bearings may pass through it witho t touching it. This rod is used to apply manual or electromagnetic pressure to the cover. Operation of this red opens and closes the cover and satisfactorily permi's the sending of sharp and distinctive signals, the periods between which are sufiiciently silent for all the above mentioned us s.

The use of a cover such as described has the further advantage of completely protecting the rotor and stator from the atmosphere and so preventing the fouling and corrosion which frequently prevent sirens from operating.

Other parts of the invention are embodied in a typical form which will now be described with reference to the accompanying drawings, the parts of the invention for which patent protection is desired being those delimited by the claims.

In the drawings-' Fig. 1 is a central vertical section and Fig. 2 is a section on the line H, II of Fig. 1.

An outer case I houses an electric motor consisting of field yoke 2 and rotor 3. The hollow rotor shaft 4 is mounted in bearings and 6 and is extended to carry the siren rotor 8, which runs in the stator 9. The stator 9 has a cover In with a central intake I I and is provided with air outlet ports I 2.

An operating lever l3 operates through spindle l4 and lever arm [5 to lift a central push rod I6 and at the same time closes the circuit to the electric motor through contacts I! and I8 and contact bridge l9.

The cover 2E! is adapted completely to envelop the siren stator and rotor and is formed at its lower margin 2| to seat upon a seating 22 surrounding the lower part of the stator. It is provided with a central sleeve 23 which slides upon :a hollow vertical guide pin 24 formed with its supporting spider arms 25 as part of the stator cover lit. A valve plate 25 is mounted on the sleeve 23 and is lightly pressed by a spring 21, so as to seat over the suction inlet ll just before the rim 2i of the cover 29 seats on the seating 22.

The cover 26 has an adjustable abutment screw 28 arranged to be engaged by the upper end of the push rod It. At the bottom of the guide pin 24 an enlargement 29 covers the open end of the shaft 4, forming a labyrinth to prevent rain or spray from entering.

A return spring 31 acts upon a lever arm 36 mounted on spindle I 4.

In operation, outward movement of lever I3 actuates push rod 16 and at the same time starts the electric motor. The upward movement of push rod It raises the cover and lifts valve plate 26. This allows air to pass freely into the suction intake 25, to pass through the rotor 8 and be thrown out of the ports [2 by centrifugal force. Releasing the lever i3 allows the return spring 3| to assist the gravity pull and the suction pull upon the cover and valve plate to return the parts to the position shown in the drawings.

Although the current is cut oif from the motor, the inertia of the moving parts keeps the sound rotor running at a high speed for a little while. During this time there is a considerable negative pressure at the rotor intake. This allows atmospheric pressure to act on the cover and on the inlet valve plate and increases very considerably the speed at which the cover descends. Since all c rculation of air within the siren rotor is prevented by the closing of the valve plate and all egress of air is prevented by the cover closing upon seating 22, no noise will be heard at this time.

Clearly various structural modifications can be made without depart ng from the scope of the invention in its w der aspects. For example, while the central hollow guide pin has the advantage of protecting the sliding surfaces from exposure to the Weather in a convenient manner and avoids any tendency of the cover to stick in case it tends to swing (for example when a ship is rolling), it is possible to use any number of guides in appropriate positions. The movement of the cover can also be arranged in various ways, either by pressure applied centrally through a hollow shaft from below as shown or from above or at a number of points adjacent to the periphery.

I claim:

1. A siren giving sharp tones of short duration comprising a rotor having radial blades with a rim, a stator having a rim and an air suction Opening, the rim of the rotor and the rim of the stator having an equal number of ports, the ports of the stator rim serving as air discharge openings, and operating means comprising contacting parts forming an imperforate closure enveloping at clearance distance both the suction and the discharge portions of the stator and rotor and completing a substantially soundproof enclosure thereof, and means to effect the relative movement between parts of the closure for the free flow of air into and through the siren.

2. A siren as set forth in claim 1, wherein the rim of the stator provides a seat, and said operating means includes a movable imperforate cover adapted in one position to close against said seat and thus complete the substantially soundproof enclosure, and sa d cover in another position exposing said suction and discharge portions so that free air may flow into and through the siren.

3. A siren giving sharp tones of short duration comprising substantially radial blades and a rim, a stator having a rim and an a r suction opening, the rim of the rotor and the rim of the stator having an equal number of ports, the ports of the stator rim serving as air discharge openings, operating means including a cover adapted to surround and enclose in a substantially soundproof manner the rim of the stator at a little distance therefrom means to closely seal the suc tion openng. and means to move the cover and sealing means to permit free air flow into and through the siren.

4. A siren giving sharp tones of short duration comprising substantially radial blades and a rim,

a stator having a rim and an air suction opening, the rim of the rotor and the rim of the stator having an equal number of ports, the ports of the stator rim serving as air discharge openings, said rotor having a hollow shaft, a seating element outside of the stator, a movable imperforate cover completely enveloping the rotor and the stator at a little distance therefrom in a substantally soundproof manner and seating against said seatng element, a push rod extendng through said shaft, sa d rod having means engaging said cover, and means to operate the rod causing it to raise the cover from the seating element by virtue of said engaging means.

5. A siren as set forth in claim 4, and a valve adapted to close the suct on opening, said valve being spring biased towards the suction opening.

6. A siren as set forth in claim 4, including an electric switch means operated by the cover operating means to control the operation of the rotor in timed accord with the opening and closing movement of the cover.

ERNEST STUART RUSSELL.

REFIEBENS CITED The fol owing references are of record in the file of this patent:

UNITED STATES PATENTS Num er Name Date 1,985,954 Settegast Jan. 1, 1935 2 028,465 Middleton Jan. 21, 1936 2,074,263 Harris, Jr., et a1. Mar. 16, 1937 

